Spur Gear Cutting Formulae

[craigp85]

Hi all i am new to this forum, my situtation is i am trying to design a spur gear profile for our wire cutter so that we can cut an electrode to spark the porfile of our gear onto the component.

The module is 0.75 and the number of teeth are 41, how the heck do you work out the angle of the teeth etc i think our pressure angle is 20degrees, please help and when i work out my circumference pitch is seems to be way out!!!

My calculations so far:

CP = 2.3562....i get 8.78???
Module = 0.75
PD = 30.75
Addendum = 0.75
Dedendum = 0.8745
Total depth of tooth = 1.625
Tooth thickness = 1.178
OD = 32.25
ID = 29

 

[craigp85]

Ok hold on so a bit of a blonde moment obviously 2.3562 is mm per tooth not angle, but still my distance per tooth measures 2.46 not 2.36???

 

[L17Aurora]

CP=Mn x PI = 2.3565
email me for a geometry program mikebull@blueyonder.co.uk

 

[craigp85]

Hi L17Aurora, i realise that the CP = 2.3565, but if i make it that then it seems to look way out as there ends up being almost enough to fit 2 more teeth?!!!

I am using solidworks 2008 to design the gear.

I have included a picture to help explain what i mean.

Thanks

 

[PeteDB]

craigp85,
The CP is measured at the PD (not the OD) Your tooth thickness at the tip should be .572mm. Your base diameter (BD) is PD*cos(20)=28.8955mm. This is the diameter that you would unwind a string to generate the involute profile. You said nothing about the gear this will mate with. This gear mated with itself on standard centers would have zero backlash. Which is not a recommended practice.

 

[lbmakem]

hi
multiply the following by your module:
OD= teeth +2
PCD= teeth
add = 1
basic tooth thickness= 1.5708
the depth of tooth depends on the standard you are working too,the common one is 2.25


cp= (3.141592*module)/ 25.4
ded= depth - add
for a 41 tooth gear of .75 module the OD = 32.25mm, PCD= 30.75mm,ADD=.75mm,T.TH=1.1781 and the depth=1.6875.
hope this helps

 

[gearcutter]

Circular pitch is measured around the circumference of the pitch diameter, not as a chord on the outside diameter as you show in your illustration.
SolidWorks usually has a toolbox that generates involute gears & splines. What version are you using?


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[craigp85]

Hi guys thanks for your input, gearcutter i am using Solidworks 2008.

 

[PeteDB]

Be aware. The Toolbox gears in Solidworks are representations for machine design purposes. They are not true involute gears that you can use for manufacturing.